This version (05 Feb 2014 19:02) was approved by Lars-Peter Clausen.The Previously approved version (13 Nov 2012 15:22) is available.Diff

Supported Devices

Evaluation Boards


The AD7991/AD7995/AD7999 are 12-/10-/8-bit, low power, successive approximation ADCs with an I2C®-compatible interface. Each part operates from a single 2.7 V to 5.5 V power supply and features a 1 μs conversion time.

Each AD7991/AD7995/AD7999 provides a 2-wire serial interface compatible with I2C interfaces. The AD7991 and AD7995 come in two versions and each version has an individual I2C address (see Table 8 of data sheet for address and part number selection). This allows two of the same devices to be connected to the same I2C bus. Both versions support standard, fast, and high speed I2C interface modes. The AD7999 comes in one version.

The AD7991/AD7995/AD7999 normally remain in a shutdown state, powering up only for conversions. The conversion process is controlled by a command mode, during which each I2C read operation initiates a conversion and returns the result over the I2C bus.

When four channels are used as analog inputs, the reference for the part is taken from VDD; this allows the widest dynamic input range to the ADC. Therefore, the analog input range to the ADC is 0 V to VDD. An external reference, applied through the VIN3/VREF input, can also be used with this part.


  • System Monitoring
  • Battery Powered Systems
  • Data Acquisition
  • Medical Instruments

01 Oct 2012 09:58 · Dragos Bogdan

The goal of this project (Microcontroller No-OS) is to be able to provide reference projects for lower end processors, which can't run Linux, or aren't running a specific operating system, to help those customers using microcontrollers with ADI parts. Here you can find a generic driver which can be used as a base for any microcontroller platform and also specific drivers for different microcontroller platforms.

Driver Description

The driver contains two parts:

  • The driver for the AD799x part, which may be used, without modifications, with any microcontroller.
  • The Communication Driver, where the specific communication functions for the desired type of processor and communication protocol have to be implemented. This driver implements the communication with the device and hides the actual details of the communication protocol to the ADI driver.

The Communication Driver has a standard interface, so the AD799x driver can be used exactly as it is provided.

There are three functions which are called by the AD799x driver:

  • I2C_Init() – initializes the communication peripheral.
  • I2C_Write() – writes data to the device.
  • I2C_Read() – reads data from the device.

I2C driver architecture

The following functions are implemented in this version of AD799x driver:

Function Description
char AD799x_Init(char partNumber, char deviceVersion) Initializes I2C.
void AD799x_SetConfigurationReg(unsigned char registerValue) Writes data into the Configuration Register.
void AD799x_GetConversionResult(short* convValue, char* channel) Reads the High byte and the Low byte of the conversion.
float AD799x_ConvertToVolts(short rawSample, float vRef) Converts a raw sample to volts.
resources/tools-software/uc-drivers/ad7991.txt · Last modified: 10 Jul 2013 14:42 by Lucian Sin